Conversion of hydrocarbon oils



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QVERSION 9F HYDHOCARBON OILS Filed May 1,9,L :931

ma ZM INVENTOR @www ATTORNEY UNITED STATES PATENT OFFICE 2,037,952CONVERSION OF HYDROCARBON OILS Richard F. Trow,

The Texas Company, poration of Delaware Port Arthur, Tex., assignor toNew York, N. Y., a cor- Application May 19, 1931, Serial No. 538,591

1 Claim.

This invention relates to the conversion of higher boiling hydrocarbonoils into lower boiling ones and relates of treating a charge yield ofmotor fuel distillate havi knock value and densable gas and heavyresidue particularly to a method oil to produce a maximum ng a highantia minimum yield of non-conwhiclr contains little or no convertibleconstituents.

The invention broadly contemplates a method of cracking Ipetroleum oilsto ultimate yield, so-

called because uncracked portions of the charge oil or such fractionsproduced in recycled and further cracked, and

the process are ultimately only a desirable distillate, a small quantityof gas and a relatively heavy pitch-like residue is delivered from thesystem.

According to my invention a relatively dirty higher boiling oil, such asunclean gas oil or topped crude, may be heated by heat interchange withhot vaporous products from the reaction zone and/or in a heating coil tocosity and distill off a fraction,

break the Visrelatively clean gas oil while clean recycle oils may beremoved by reflux condensation from the hot vaporous products and byflash distillation from residual portions developed in the cracking stepand the clean oils combined to form a stock.

clean cracking In the past a preference has been shown for the the gasoil treating separately from crude oil and fresh gas oil fractionsfractions from residues developed in cracking operations, which are of amore refractory nature, in such manner as would be most effective toeach. For example,

a fresh gas oil may have been cracked in the liquid phase andsatisfactory yields of motor fuel obtained with a minimum production ofgas,

while a gas oil from cracked residues, which would probably not besusceptible to conversion under the mild conditions of liquid phasecracking, may

phase and satisfactory yields nimum producliquid phase process usuallyproduces a considerable quantity of coke and the .anti-knock value ofthe motor fuel is low while a vapor phase process usually produces aAconsiderable quantity of non-condensable gas.

Recently there has come into use in the refining industry a crackingprocedure generally known as low liquid level cracking. This method isgenerally characterized by the use of lower temperatures but longer timeof digest under heat ofthe vapors, as compared with vapor phasecracking, While at the same are higher and the time of diges time thetemperatures t under heat of the liquid oil is shorter than in liquidphase cracking. As will become apparent hereinafter, my inventioncomprises certain improvements in this general type of operation.

As previously stated I prefer to combine the 5 clean gas oil fractionsfrom the cracking step in the system and that from the charge oil andsubject them together to suitable cracking conditions to produce anultimate yield of motor fuel from the charge oil. As such a, crackingstock 10 will contain both relatively highly refractory and lessrefractory constituents it is particularly advantageous to process itunder conditions of 10W liquid level cracking Where the more refractoryconstituents become vaporized and are subjected 15 to slightly longertime of digest than the less refractory constituents, most of whichremain liquid, with the result that minimum percentages ofnon-condensable gas and pitch or coke are produced.

Where charging topped crude or an oil of greater viscosity than theusual gas oil it is preferable to subject it to a sufciently hightemperature in the initial stages of heating to break or reduce theviscosity somewhat and thus 25 make available an additional amount ofthe charge as a cracking stock.

These and other objects and advantages of my invention will be betterunderstood by referring to the following description taken in connection30 with the accompanying drawing, the single figure of which illustratesin diagrammatical elevation a preferred embodiment of apparatus adaptedto practice the invention.

Element I is a furnace, 2 and 3 are reaction 35 vessels, 4 is adephlegmator, 5 is a reflux condenser, 6 is a final condenser, 1 is atrap and 8 is an accumulator drum, which constitutes the main items ofthe cracking portion of the apparatus.

Element I0 is a combination still and dephlegmator, II is a condenser,i2 is a trap, and I3 is an accumulator, which constitutes the main itemsof the sensible heat or autogenous distillation Zone in which the cleancracking stock is de- 45 veloped and from which an uncrackable residueis released from the system and a small quantity of desirable distillateis fractionated out.

A charge line I5 may lead through a preheater coil I6 situated in refluxcondenser 5 into a vapor 50 line 51 which connects the upper portion ofthe vessel 3 with the lower portion of the dephlegmator 4 or bymanipulation of valves 20, ZI, 22 and 23 may lead through I6 to a heatercoil 26 or bypass I6 or a combination `of the three.

A line 25 connects the lower portion of the dephlegmator 4 with theheater coil 26 which is preferably situated in the upper portion of thefurnace I. By manipulation of the valves 21 and 28 the coil 26 may beby-passed and a direct connection effected with the lower portion of thecombination vessel I0.

Drain lines 30 and 3| lead from the bottoms of vessels 2 and 3 to a mainline 32 connecting with the lower portion of the still section of thevessel I0. A vapor line 35 connects the lower or still section with theupper or dephlegmating section of the vessel I and a release line 36leads from the bottom of the lower section of this vessel.

A vapor line 40 connects the dephlegmating section with the condenser IIand a line 4I connects the condenser I I with the trap I2. A pump 43takes suction from the trap I2 through a line 42 and discharges into theupper portion of the dephlegmating section through a line 44. A line 45connects the condenser II with the accumul-ator I3 which has a liquidoutlet 46 and a gas outlet 41.

A pump 50 takes suction from the lower portion of the dephlegmatingsection of vessel I0 through a line 49 and discharges through a, line 52into a heater coil 53 situated in the lower portion of the furnace I. Abranch line I leads from the discharge line 52 into the upper portion ofthe still section of I0 onto the uppermost of a series of baiilessituated therein.

A line 55 connects the heater coil 53 with the first reaction vessel 2and a line 56 connects the lower portion of the vessel 2 with the lowerportion of the Vessel 3. The vapor line 51 leads from the upper portionof the vessel 3 to the lower portion of the ldephlegmator 4 aspreviously mentioned.

A vapor line 60 connects the upper portion of the dephlegmator 4 withthe lower portion of the reux condenser 5 as does also a run back line6I. A nal vapor line 62 leads from the reflux condenser 5 to the nalcondenser 6. A line 63 connects the final condenser 6 with the trap 1from which a pump 65 takes suction through a line 64 and discharges thrua line 66 into the upper portion of the dephlegmator 4. A line 61connects the trap 1 with the accumulator 8, which has a liquid outlet 68and a g-as outlet 69.

When beginning to operate, a suiicient amount of clean oil may be drawnin thru a pipe 48 from a source not shown and pumped into the heater 53.After operating conditions are established a switch may be made andfresh charge oil supplied to the system thru the line I5.

In a preferred mode of operation a fresh charge oil which may be atopped crude oil is charged thru the preheater I6 and emerging therefromat a temperature of approximately 450 F. is delivered into the vaporline 51 near its connection to the lower portion of the dephlegmator 4.'I'he thus commingled cooler charge oil and hot vaporous products fromthe reaction zone undergo heat interchange by which a portion of thefresh charge may be vaporized while the remainder, with refluxcondensate resulting from the dephlegmation of the vaporous products isdeposited in the bottom of the dephlegmator. The liquid being depositedin the dephlegmator is regularly discharged therefrom at approximatelyri50 F. and may be passed thru a heater coil 26 in the upper portion ofthe furnace I or may be passed direct to the lower portion of the stillsection of the vessel I0.

In some instances it may be found preferable to heat the fresh chargeoil alone and to deliver the reilux condensate in dephlegmator 4 directto the flash distillation zone. Thus the fresh charge may be passedthrough the heaters I6 and 26 and merging with the reflux condensatenear the entrance be delivered into the lower section of the vessel I0.

While the heater coil 26 is shown Iand described as being situated inthe upper portion o-f the furnace I it is pointed out that it may bepreferable to situate it in a separate furnace where the heating couldbe regulated independently. Such an arrangement as this is of advantagewhere the fresh charge is of relatively high viscosity and it isdesirable to raise the temperature high enough to break or reduce theviscosity by effecting a small amount of cracking. For example, a toppedcrude which may have a viscosity of approximately 400 universal at 100F. when treated in this manner will be reduced to approximately 100 at100 F.

The purpose of breaking the viscosity is to develop and extract themaximum percent of gas oil from the fresh charge. Frequently enough heatto accomplish the desired result can be imparted to the charge oil inthe coil I6 and in the line 51. This is not true, however, of all stocksnor all operating conditions consequently the heater coil 26 is providedin which the charge oil may be heated to the desirable temperature.

Residue collecting in the bottoms of the vessels 2 and 3 may be releasedtherefrom at a temperature of the order of 850 F., and is conducted intothe lower portion of the still section of the vessel I0.

The combined charge and recycle oil from the dephlegmator 4 and theresidue from the vessels 2 and 3 are subjected to autogenousdistillation in the vessel I0 under a slightly or greatly reducedpressure and the resulting vapors moving upwardly are scrubbed by thedownwardly moving liquid reiluxed to the top of the series of bailles.The resulting clean vapors are conducted thru the line 35 into thedephlegmating section of the vessel I0, while a heavy residue collectingin the bottom of the still section is released as desired.

The liquid delivered to the upper of the series of baiiles is a portionof that liquid accumulating in the dephlegmating section and isaccordingly itself a clean scrubbed fraction. The amount of this liquidis just suiiicient to effect a desirable scrubbing of the new vapors andis in turn revaporized by the heat of these vapors and with them isreturned to the dephlegmating section thru the line 35.

The clean cracking stock thus developed is withdrawn from the lowerportion of the dephlegmating section of vessel I 0 and is passed thruthe heating coil 53. Emerging therefrom at a temperature ofapproximately 950 F. it is conducted into the upper portion of thereaction vessel 2, which is preferably maintained at a pressure ofapproximately 400 pounds per square inch, as is the remainder of thesystem except the autogenous distillation portion.

There is a certain amount of cracking effected in the coil and a portionof the oil becomes vaporized therein. The heated products transferredfrom the coil into the upper portion of the vessel 2 at relatively highvelocity are further vaporized therein and the vapors are passed thruthe vessel 2 and into the vessel 3 by the connecting line 56.

Remaining vapors emerge'from the upper portion of the vessel 3 whileliquid portions depositing in the bottoms of the vessels 2 and 3 arepreferably kept drawn down lo-w so as to prevent collection ofsubstantial bodies of liquid therein.

The liquid portion of the heated oil is subjected to just such time ofdigest in the vessel 2 as is required for the liquid to move from theentrance pipe 55 to the outlet pipe 30. A certain amount of the liquidparticles are carried into the vessel 3 and this portion has anadditional time of reaction which lasts until it is deposited andwithdrawn thru the pipe 3l. The vapors are subjected to a time of digestin the system running from the instant they are formed until they arequenched by the entering charge in the vapor line 51.

The oil which condenses and remains condensed in the vessels 2 and 3 isdeposited in the bottoms thereof and released thru the lines and 3| tothe main line 32 to be eventually discharged into the lower portion ofthe still section of vessel Iii. It is preferable to reduce the pressureon the residue as soon as it leaves the reaction vessels to a suicientextent to effect a desirable temperature reduction of the o-il by theresultant expansion or distillation. In other words a sufficient time ofreaction is provided for the liquid in the vessels and it is notdesirable to allow a prolongation of the cracking conditions after theresidue leaves the vessels.

The vapors emerging from the vessel 3 are conveyed thru the line 51,wherein the fresh charge is delivered from the line l5, and by heatinterchange serve to warm up the fresh charge and to cool the hotvapors.

The vapors, and combined fresh charge, are conducted to the dephlegmator4, and are therein subjected to any conventional method offractionation. A portion condensed from the vapors and a portionremaining condensed from the fresh charge in the dephlegmator 4 isdischarged therefrom thru the line 25 and, according to the nature ofthe charge stock, is passed thru the heater coil 26 or is delivereddirect into the lower portion of the still section of vessel l underreduced pressure as previously described.

The vapors dephlegmated in 4 are passed thru the reflux condenser 5where remaining heavier portions are condensed and a portion of theirheat is imparted to the fresh charge which is being passed to the coilI6. The nal vapor is conducted thru the line 62 to condenser 6 and nallyto storage. 'Ihe portion condensed in the condenser 5 is returned to theupper portion of the dephlegmator 4 thru the line 6I as is also aportion condensed in the condenser 6 and trapped out in the trap 'I as areflux cooling medium.

A suitable clean cracking stock for passing heating coil 53 may be a gasoil having a straw or light straw color or an oil of I5-20 on the 1/2cell, Lovibond scale; however, the use in this stage of other relativelyclean cracking stocks is not precluded.

While a preferred mode of operation has been described herein in detailit is to be understood that neither this form nor the approximatetemperatures given are intended to serve as a limitation to the spiritand scope of my invention which is believed to be adequately defined andlimited by the appended claims.

I claim:

The method of converting relatively viscous petroleum oil to a mo-torfuel and to pitch-like residue in a combined distilling and crackingoperation, which comprises heating the fresh oil to a mild crackingtemperature to materially reduce the viscosity thereof while maintainingsuch pressure on the oil as to prevent vaporization of the more viscousconstituents, flashing the viscosity-broken stream in a zone of lowerpressure wherein separation of vapors and pitch-like residue occurs,passing the separated vapors to a fractionating zone and fractionatingthe vapors therein to recover a clean gas oil condensate therefrom,subjecting the gas-oil condensate to a relatively high crackingtemperature while in transit through a confined heating zone,discharging the cracked products into an enlarged reaction zonemaintained at cracking temperature under superatmospheric pressurewherein separation of liquid and vapors occurs, withdrawing liquid fromsaid enlarged cracking Zone at a rate adequate to prevent accumulationof liquid therein and flashing the withdrawn liquid into saidlow-pressure flashing Zone, withdrawing vapors from said enlargedreaction Zone, dephlegmating and fractionating them to produce a finallight motor-fuel distillate and a heavier condensate and delivering saidheavier condensate to said low-pressure flashing zone.

RICHARD F. I'ROW.

